The present invention relates broadly to a threshold detector apparatus, and in particular to a radiation upset threshold detector apparatus.
When an electronic device utilizing semiconductors is operated in an environment which is subjected to radiation such as gamma rays, hole electron pairs are generated within the semiconductor material. These carriers move by diffusion and drift to and through the semiconductor junctions. The effect of these carriers passing through the semiconductor junction is to produce transient photocurrents. The current components which enter the base region are called the primary photocurrents. The major component of primary photocurrent is produced in the collector region and in the transition region of the collector-base junction. The emitter component of the primary photocurrent is, in general, substantially smaller than the major component of the primary photocurrent. The short diffusion length which is utilized in the emitter contributes to the smaller emitter component of the primary photocurrent.
In the prior art, the measurement of radiation-induced photocurrents in semi-conductor circuits was at best very difficult and subject to gross discrepancies. This is due to the fact that the instruments or devices which are utilized to make the photocurrent measurements are themselves subjected to and affected by the radiation conditions that produce the photocurrents in the semi-conductor devices. The present invention provides a method of photocurrent measurement which is simple and accurate.